The invention relates to a method of sealing the front cylindrical portion of a sleeve body of a practice cartridge wherein a predetermined number of radial inside and outside folds are created in the forward region of the sleeve body in two work cycles, and wherein circular arc-shaped inside folds of a predetermined radial depth are created during the first work cycle by exerting radial pressure on an outer surface of the cylindrical sleeve body using corresponding shaped profiling tools.
Practice cartridges in which the forward region of the sleeve body, which as a rule has the shape of a projectile bursting body, are closed by folding are known from numerous patent documents (e.g. British Reference No. GB 277,762, and German Reference Nos. DE 1,138,341, DE 1,082,162 and DE-OS 4,128,050). In these cases, the folding is typically effected in a single work cycle, in which the cylindrical tip or forward section or region of the sleeve body is pressed in at, for example, six locations at the circumference by radially inwardly-closing profiling stamps or tools until the inside folds being formed touch lightly in the interior. The opening that may remain between the inside folds can then be sealed subsequently by the application of a water-insoluble varnish.
Practical experiments have shown that a method of this type leads to poor firing results, because with a large number of folds the width of the profiling stamp must be relatively narrow. However, such a narrow stamp results in the region of the inside folds being subjected to a severe material stress and, possibly, even crack formation. If, on the other hand, the profiling stamps are configured to be wider and to have a preferably arc-shaped profile, a relatively large opening remains between the inside folds, and sealing this opening by means of a varnish gives rise to problems.
A method in which the sleeve body is closed by fold formation in two work cycles is further known from German published patent application No. DE-AS 1,159,379. In the first work cycle, a relatively small number of circular arc-shaped inside folds are created and brought into contact with one another. In the subsequent, second work cycle, the outside folds, by means of an ogival, concave die and the application of an axial pressure, are flattened, are broadened laterally and are pressed together in such a way that two lateral folds describing part of a circular arc in cross-section are formed from each outside fold, with these lateral folds tapering toward the end, and together forming an ogive.
Aside from the fact that this method is relatively expensive, it has the disadvantage that slight partial deformations can occur during production that have a negative influence on the function of the training cartridge and can lead to jamming in the weapon barrel. In particular, the division of the outside folds into lateral folds is associated with considerable problems.
It is therefore the object of the invention to disclose a method of the type mentioned at the outset which permits a simple and thus cost-effective way of closing or sealing the cartridge body, and in particular the front region of the cylindrical sleeve body by folding without resulting in predetermined fracture points in the region of the inside folds during closing or sealing.